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Manufacture an helical auger flight from steel plate
4

Manufacture an helical auger flight from steel plate

Manufacture an helical auger flight from steel plate

(OP)
Hello,

I'm trying to manufacture a steel auger flight these are to be screwed into the ground and act as an anchor, the outside diameter of the flight is 700mm and 20mm thick and are to be welded to a 90mm diameter shaft and the pitch is 125mm.

I'm wondering how to manufacture these auger flights.  I know the plate is cut with a profile burner but how do a get it to the helical auger shape?
 

RE: Manufacture an helical auger flight from steel plate

I think each pitch is a complete circle. They are then pressed apart & welded up. google Srew feeder/auger etc.
 

RE: Manufacture an helical auger flight from steel plate

(OP)
Yeah I'm neally 100% sure the first step is to cut a circle and the diameter would be a bit bigger ie od = [(700^2)+(125^2)]^0.5 = 711mm and the id is alos a bit bigger [(90^2)+(125^2)]^0.5 = 154mm.  I'm guessing they are pressed a part just a bit more than the pitch to allow for sring back - i'm wondering if any one has come accross a machine that will do this.

RE: Manufacture an helical auger flight from steel plate

To achieve a circular auger section after 'twisting', both the outer and inner profiles of the flat blank would need to be elliptical.

RE: Manufacture an helical auger flight from steel plate

(OP)
I'm pretty sure they are just two circles.

RE: Manufacture an helical auger flight from steel plate

Circles would probably be good enough for a ground anchor auger, but as a test, cut the split circular shape from a piece of card, twist it, and note what happens.

RE: Manufacture an helical auger flight from steel plate

(OP)
I must try the card.  It's getting the cut steel split circles into the helical shape that i can't figure out.

RE: Manufacture an helical auger flight from steel plate

It is simple really. It is an ellipse with the smaller diameter given by the diameter of the auger and the large diameter given by the square root of the diameter squared plus the pitch squared

RE: Manufacture an helical auger flight from steel plate

(OP)
You would think it would have to be an ellipse but i'm 99% sure its just two circles the od is square root of od squared plus pitch sqaured and the id is sqaure root of id squared plus pitch sqaured.  This then gives me a flat spilt ring plate - how do i get this into a helicoil shape you would think there bound to be a machine that can do this.

RE: Manufacture an helical auger flight from steel plate

You could use a regular brake press, bumping the blank with many angular hits. this would give a multi-faceted surface though. Again, probably good enough for a ground anchor.

If you need a smooth surface, you will probably have to use a more specialised tapered-roll rolling machine.

 

RE: Manufacture an helical auger flight from steel plate

(OP)
Yeah I think an ordinary press brake would do the job - only thing is I have 200 of these to make and it would be very slow and they would all be slightly different just look very amateur.  I was thinking of a former type template then place in the split ring on it and and then  press it between to formers.  But I'm thinking the split ring would then lie along the slope of the former and not press right.  There is a machine that can roll flat strip into into a helicoil shape but it will not do my job as there far to big a difference in the radius's the strip would simply tear as it was being rolled - heating would be no good even if it did work as the would then be far to thin.

RE: Manufacture an helical auger flight from steel plate

You can develop some shapes, such as a cone, from flat plate and all it requires is bending the plate.  Other shapes, such as a sphere, will require actually stretching or compressing the plate in areas to form the shape.  I think an auger screw is going to fall into the second category.  You won't know the exact shape to cut without some trial and error, and it would depend on the forming process as well.  The force required to form the plate will be a lot greater than a bending-only process as well.  It might be easier to do the forming hot.  I would guess that the people that make smaller auger screws have specialized forming machines for the job.  Larger ones might be done on a hydraulic press.   

RE: Manufacture an helical auger flight from steel plate

Everybody has missed a point: A helicoid is not developable!
A closely related surface appropriately called a "developable helicoid" exists. The straight line elements are not radial as in the helicoid, but are tangent to the inner cylinder. A real excercise in descriptive geometry. I think descriptive geometry is not taught any more.

RE: Manufacture an helical auger flight from steel plate

Different manufacturing techniques are required for different designs. Since your application is a ground anchor, I assume that you only need one turn. Thus you can make it from plate. The I.D. would be an ellipse with the minor axis about equal to your tube. The major axis would be the tube diameter divided by the cosine (I think) of you helix angle. Since you want a uniform flight height the O.D. will be the I.D. plus the height. Cut that from plate, cut the ellipse open along the major axis, then bend and twist.  

RE: Manufacture an helical auger flight from steel plate


15EA,

The auger you describe is quite a serious bit of bending and welding; can't you get them made for you by someone who already makes helical earth anchors and has all the right equipment and knowledge, I expect something this size is probably quite small in the offshore oil industry. It may be worth searching for something there or looking at helical foundation piles which are very similar apart from reversing the axial load.  Like here>

http://www.foundationsupportworks.com/foundation-repair/helical-pier-systems/technical-helical-pile.php

If you must make them yourself, have you considered making a wooden pattern and getting them cast in steel?
 

RE: Manufacture an helical auger flight from steel plate

(OP)
I know it going to require a bit of heavy duty cutting and welding - I'm looking forword to getting started on this project.  I'm 99.99% sure to create the sectional helical shape I need to cut two concentric circles - the formaula for 700 od and 90mm tube and 125mm pitch is plate od = [(700^2)+(125^2)]^0.5 = 711mm and the plate id is also a bit bigger [(90^2)+(125^2)]^0.5 = 154mm.  Note each secation helicoil will be approx 350 degrees or so.  But how do i get this in to the helical (helicoid) shape.   

RE: Manufacture an helical auger flight from steel plate

(OP)
Yeah its a common enough item you see them everywere, but i can't see a machine that can make them.

RE: Manufacture an helical auger flight from steel plate

15EA
I used to make these screw flights for a living, and my advice is:  Buy them from somebody already making them.
 Try Screw conveyor corp  in Hammond Illinois  http://www.screwconveyor.com/productline.htm
  The starter flights for their screw lifts are close to the diameter and pitch you require.
 If you are determined to make them, a cast  or CNC machined die set, formed to the correct helix, and set in an OBI punch press inclined back as far as you can get it, will do the job. Even then you may need to hot form them.
 You may however need more than 200 flights to recover the cost of the tooling.
B.E.

RE: Manufacture an helical auger flight from steel plate

In its simplest form, cut a 700mm circle. Now cut a 90 mm circle out of the center.  You now have an annulus. Cut a straight line through the annular plate from the ID to the OD. Raise one side of the cut 125mm relative to the other and weld along the ID onto the 90mm stem.  You now have one flight of your auger.

RE: Manufacture an helical auger flight from steel plate

berkshire,
thanks for waking me up. 20mm thick auger can be cast with ease. I have been casting augers in different alloys for road pavers,screw conveyors,a  continuous annealing furnace retort for cartridge brass,etc. One flight is formed in a sheet metal,by stretch forming manually .This is used as a master for making patterns  

Learn the rules,so you know how to break them properly.
Dalai Lama

_____________________________________
 

RE: Manufacture an helical auger flight from steel plate

arunmrao (Materials)
You know I had not thought of that, I was thinking of the forming die.
  But now that you mention it, Malleable cast iron would work pretty well. Also a traditional wooden foundry pattern can be done today on a CNC router for not too much cost.
B.E.

RE: Manufacture an helical auger flight from steel plate

All grades of wear resistant steels,alloy irons,stainless steels are being cast by me. Malleable iron,one rarely hears of them.Large horizontal lathes are used for turning the wood piece.

Learn the rules,so you know how to break them properly.
Dalai Lama

_____________________________________
 

RE: Manufacture an helical auger flight from steel plate

(OP)
Sounds like to make a sectional flight its a case of cut out slit ring from a steel plate.  Then put the plate in press and push against a die type former and with a bit of trail and error i'm sure this will work.  Thanks for you helpful comments.

RE: Manufacture an helical auger flight from steel plate

15EA (Geotechnical)
That's about it, cut your slit ring, put it in the forming die and work the part around. Do not try to do it all at once, or it will distort.Make sure your die set has a short spigot to hold the inside shaft diameter true. Your tonnages will be high because you are going to be stretching 20mm thick material.

 You might want to check out arunmrao's casting methods, they may be more cost effective.
B.E.

RE: Manufacture an helical auger flight from steel plate

(OP)
berkshire,

I think your right - what would you you suggest I make the die set of would mild steel do.

In relation to casting I think it would be to expensive.

RE: Manufacture an helical auger flight from steel plate

15EA
I think you will need something a little tougher than mild steel, or you will get distortion in your die set. I am not a tool and Die maker so I cannot advise you there.
B.E.

RE: Manufacture an helical auger flight from steel plate

(OP)
berkshire,

I'm only making 200 number - sure if it gives me trouble its easy enough to repair and if i need better quality i can do that later.

RE: Manufacture an helical auger flight from steel plate

15EA (Geotechnical),

First let me point out that I have no experience with soil anchors.  However, I have seen quite a few auger type lifting screws made by the type of ad hoc methods described in many web articles and basically the same as you are intending to try, and they were very good for lifting loose particulate material, however, despite being made from "easy" light-gauge sheet metal, few approached the true helical form required for easy driving and ultimate resistance to "Pull-out" forces in compacted soil. Maybe the type of subsoil your anchors will encounter will be forgiving of these pitch and form errors.

I know you said that you were looking forward to this project and that you think that a casting (the best bet I think) would be too expensive, but the fabricated route will not be easy and 200 is going to be quite a chore!

BTW, a standard CD makes quick model to get the feel for the geometry, the bore and OD are close to one sixth scale and it's easy to score a radial line and snap it to represent your starting blank. Now you have to pull up on one side of the cut and get it to lie 21mm and parallel to the other side to avoid the "Duckbill" errors illustrated in my previous link above, it's not that easy, bearing in mind that it really should be three times thicker to be to the same scale!

If it were me, I would try and by them from a specialist, but I wish you the best of luck!
 

RE: Manufacture an helical auger flight from steel plate

From a long time ago.

You will have to make the inner diameter of your flights slightly larger as it will go eliptical when you pull it for your pitch.

If I recall we always had a left and right segment when using this approach.

Have you looked at the HP requirement for your auger/screw

You might wan't to look at this this company from the banner ad on this page.

http://www.helicalpiersystems.com/?gclid=CJfki8b7l50CFcNB5godNQHcpQRusty

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